Thank you for the ideas. We do use Jetdry. I will look into an inline filter. One question. I've read that there is a rod in the hot water heater that can go out yet still heat the water. Is this a viable possibility?

Water heaters have an anode rod, which reduces corrosion inside the heater. Certain rods, combined with certain water ( often well water) can create an odor in the water. A plumber can change the anode to a different material type for that issue. If you are not on a well, this is usually NOT a problem.

Why are you using an air break in the drain line? I'm seeing alot of drain water standing in the drain line. May be holding flapper valve open in the dishwasher. Might try installed your drain line per the installation instructions and see if that doesn't help.

My first thought would be, is your drain hose high enoug?. If not, your nasty food residue will drain back into dishwasher and will create bacteria and such as to cause a funky smell. Looking at the pic of the disposal,it looks like there is not a high enough loop to stop such a problem.

Sorry, didn't see the siphon break. Could be siphoning back to washer. Eliminate siphon break, create a high loop to stop back flow.

We don't know where he lives, but many states REQUIRE the air gap connection. A high loop would minimize back flow, and of course are still allowed in some states. But since the high loop is NOT above the top of the sink, it can never completely eliminate the possibility of backflow.

I see a hammer arrester on the hot water connection, and those can fail and be an odor source...just one more possibility